The prior art embraces capping units embodied as a rotating carousel with a platform designed to carry a plurality of containers designed to hold substances of various nature including liquid food products, typically milk or fruit juices, and non-food products such as mineral lubricating oils, detergents, etc.
The containers occupy respective bays formed in the circumferential edge of the platform and are directed along a circular path from an infeed station to an outfeed station.
The carousel also presents a frame positioned above and rotatable as one with the platform, carrying a plurality of devices by which screw caps are twisted each onto the threaded neck of a relative container.
Each device is positioned above a corresponding container and presents a gripper by which a relative cap is held tight and rotated in such a way as to screw it onto the neck.
Thus, as the containers are caused to move along the circular path, the gripper of each device will approach and grip a respective screw cap, then effect the rotational movement, and finally release the cap when tightened.
In particular, the gripper is associated with a rotating shaft rendered capable of vertical motion through the agency of respective cam means, by which shaft and gripper can be moved toward and away from the cap of a relative container as the frame rotates. The cam means coincide with a stationary portion of the frame and are engaged by a following roller associated with the shaft.
The shafts are set in rotation by way of dedicated transmission systems coupled to a single motor, or alternatively, each of the screw capping devices can be equipped with a respective motor coupled directly to the shaft.
Screw capping devices are also equipped generally with a clutch, by which rotary motion is transmitted from the shaft to the gripper. As the screw cap is fully tightened and the clutch begins to slip, at the moment when the resisting torque on the gripper exceeds a prescribed value, the shaft and the gripper become uncoupled, with the result that the gripper ceases motion while the shaft continues to rotate.
At this point, the gripper opens gradually so as to release the cap, and another container can be admitted. The open-and-close movement of the gripper is produced by an actuator, guided by the movement of the shaft and acting directly on the gripper.
In reality, prior art units of the type outlined above are affected by serious drawbacks connected with the structure of the screw capping devices.
A first significant drawback derives from the lack of versatility afforded by such devices, which can be utilized only with containers having predetermined physical characteristics.
In effect, the shaft, the gripper, and the drive components operating the shaft and the gripper, are proportioned according to the height of the container and of the screw cap.
Consequently, the capping unit cannot be used to handle containers notably dissimilar one from another in terms of their physical characteristics.
Also, it will be appreciated that the device is anchored to the upper frame of the carousel, and that with multiple motion-inducing components installed, like the cam means and the means of transmitting rotation, associated respectively with the shaft and with the motor located in the carousel, the screw capping devices cannot be removed and replaced with others of different specification.
A further drawback of the unit in question derives from the structural complexity of the clutch coupling between the shaft and the gripper. Not only are the clutches composed of delicate and intricate component parts; they also contribute to an excessive bulkiness of the assembled carousel, which carries a sizeable number of capping devices.
Finally, another drawback stems from the fact that when the carousel is in rotation, the shaft of the screw capping device continues to rotate even when the cap is not engaged by the device.
In effect, when the cap has been screwed onto the respective container, the clutch will uncouple the gripper from the shaft, whereupon the shaft continues to rotate by itself until such time as the gripper engages another screw cap.
As a result, the motor, the shaft and the relative transmission components run idle for a given period during operation of the carousel, consuming energy to no good purpose.
The object of the present invention is to provide a unit for fitting screw caps to the necks of respective containers, such as will be unaffected by the drawbacks described above.
In particular, one object of the present invention is to set forth a unit with screw capping devices controllable according to the type of container being capped.
A further object of the present invention is to provide a screw capping unit that will be simple in construction, economical, suitably compact and able to suspend the rotation of components internally of the capping device.